Predictive potential of Perzyna viscoplastic modelling for granular geomaterials

Lazari, Maria; Sanavia, Lorenzo; Prisco, Claudio di; Pisanò, Federico

doi:10.1002/nag.2876

Cited by 14 publications

(3 citation statements)

References 64 publications

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“…According to the Perzyna-type viscoplastic model [27][28][29], the viscoplastic strain rate . ε vp ij can be expressed as…”

Section: Elastic-viscoplastic Constitutive Formulationmentioning

confidence: 99%

A Viscoplasticity Model for Shale Creep Behavior and Its Application on Fracture Closure and Conductivity

Li,

Zhao,

Guo

et al. 2024

Energies

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Hydraulic fracturing is the main means for developing low-permeability shale reservoirs. Whether to produce artificial fractures with sufficient conductivity is an important criterion for hydraulic fracturing evaluation. The presence of clay and organic matter in the shale gives the shale creep, which makes the shale reservoir deform with time and reduces the conductivity of the fracture. In the past, the influence of shale creep was ignored in the study of artificial fracture conductivity, or the viscoelastic model was used to predict the conductivity, which represents an inaccuracy compared to the actual situation. Based on the classical Perzyna viscoplastic model, the elasto-viscoplastic constitutive model was obtained by introducing isotropic hardening, and the model parameters were obtained by fitting the triaxial compression creep experimental data under different differential stresses. Then, the constitutive model was programmed in a software platform using the return mapping algorithm, and the model was verified through the numerical simulation of the triaxial creep experiment. Then, the creep calculation results of the viscoplastic constitutive model and the power law model were compared. Finally, the viscoplastic constitutive model was applied to the simulation of the long-term conductivity of the fracture to study the influence of creep on the fracture width, and sensitivity analysis of the influencing factors of the fracture width was carried out. The results show that the numerical calculation results of the viscoplastic model were in agreement with the experimental data. The decrease in fracture width caused by pore pressure dissipation and reservoir creep after 72 h accounts for 32.07% of the total fracture width decrease.

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“…According to the Perzyna-type viscoplastic model [27][28][29], the viscoplastic strain rate . ε vp ij can be expressed as…”

Section: Elastic-viscoplastic Constitutive Formulationmentioning

confidence: 99%

A Viscoplasticity Model for Shale Creep Behavior and Its Application on Fracture Closure and Conductivity

Li,

Zhao,

Guo

et al. 2024

Energies

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“…In this study, the time‐dependent behavior of porous rocks will be modeled through the overstress approach proposed by the pioneering work of Perzyna (Perzyna, ), which has been successfully used to reproduce the rate‐dependent characteristics of a wide range of granular solids (Di Prisco et al, ; Lazari et al, ; Tommasi et al, ; Yin et al, ). In this constitutive framework, the viscoplastic strain rate,

{\overset{ε}{true}}_{i j}^{v p}

, is computed through a viscous nucleus function Φ, which depends on the violation of the plastic constraints (i.e., on the distance between the stress state outside the elastic domain and the yield surface, often referred to as overstress):

{\overset{ε}{true}}_{i j}^{v p} = normalΦ false(f false) ([], \frac{\partial g}{\partial σ_{i j}}) .

…”

Section: Stability Criteria For Viscoplastic Solidsmentioning

confidence: 99%

Viscoplastic Interpretation of Localized Compaction Creep in Porous Rock

2019

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Recent laboratory evidence shows that compaction creep in porous rocks may develop through stages of acceleration, especially if the material is susceptible to strain localization. This paper provides a mechanical interpretation of compaction creep based on viscoplasticity and nonlinear dynamics. For this purpose, a constitutive operator describing the evolution of compaction creep is defined to evaluate the spontaneous accumulation of pore collapse within an active compaction band. This strategy enables the determination of eigenvalues associated with the stability of the response which is able to differentiate decelerating from accelerating strain. This mathematical formalism was linked to a constitutive law able to simulate compaction localization. Material point simulations were then used to identify the region of the stress space where unstable compaction creep is expected, showing that accelerating strains correspond to pulses of inelastic strain rate. Such pulses were also found in full-field numerical analyses of delayed compaction, revealing that they correspond to stages of inception and propagation of new bands across the volume of the simulated sample. These results illustrate the intimate relation between the spatial patterns of compaction and their temporal dynamics, showing that while homogeneous compaction develops with decaying rates of accumulation, localized compaction occurs through stages of accelerating deformation caused by the loss of strength taking place during the formation of a band. In addition, they provide a predictive modeling framework to simulate and explain the spatio-temporal dynamics of compaction in porous sedimentary formations.

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“…By contrast, elasto‐viscoplasticity can be used as a powerful tool to model the time‐dependent deformation, 56–60 thus simulating the delayed growth of deformation bands and the corresponding strain acceleration during creep. In this context, the so‐called overstress approach 61 (also referred to as the overstress approach) can be regarded as one of the most widely used frameworks to reproduce the time‐dependent response of a wide range of geomaterials 62–66 and regularize ill‐posed boundary value problems associated with strain softening 9,67–69 . Despite these advantages, the analytical identification of delayed localized deformation can be challenging in that the standard strain localization theory and controllability theory are not directly applicable to elasto‐viscoplasticity.…”

Section: Introductionmentioning

confidence: 99%

Strain localization criteria for viscoplastic geomaterials

Deng

Shahin

Lü

et al. 2022

Num Anal Meth Geomechanics

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This work presents a viscoplastic localization criterion to detect quasi‐instantaneous (i.e., load‐induced) and delayed (creep‐induced) strain localization in rate‐dependent solids. The study is based on the theory of controllability and a viscoplastic description of the mechanical response. Analytical precursors of unstable states are defined through systems of ordinary differential equations (OEDs). The use of the proposed criteria is illustrated at the material point level through a set of strain localization analyses simulating active strain localization of a porous rock. In addition, full‐field finite element simulations of compression tests conducted under various pressures are reported to demonstrate the role of local unstable viscoplasticity in the spontaneous propagation of deformation bands under stationary boundary conditions. The study shows that the viscoplastic localization criterion maintains a negative sign as long as the behavior is unstable, that is, the rate of deformation is accelerating. The sign switch coincides with the transition to decelerating deformation. The analyses revealed that pulses of overstress always emerge in correspondence with the growth of unstable behavior, and the peak matches the transition to stable behavior. The local responses recovered from full‐field analyses were consistent with those observed in analyses at material point level and the predictions of the presented theory.

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Predictive potential of Perzyna viscoplastic modelling for granular geomaterials

Cited by 14 publications

References 64 publications

A Viscoplasticity Model for Shale Creep Behavior and Its Application on Fracture Closure and Conductivity

A Viscoplasticity Model for Shale Creep Behavior and Its Application on Fracture Closure and Conductivity

Viscoplastic Interpretation of Localized Compaction Creep in Porous Rock

Strain localization criteria for viscoplastic geomaterials

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